This invention relates to the collection of radiant energy such as sunlight or laserlight. More particularly, the present invention is concerned with novel reflector elements that allow for the formation of a new category of light concentrating, multiple surface, primary mirrors.
A multisurface primary mirror is a type of collector that is composed of tilted mirror elements which, together, bring a large area of light to a focus upon a small receiver. These nonimaging optical systems are relatively inexpensive and easy to maintain due to their "segmented" nature. For example, if an element is broken, only that element need be replaced, rather than the entire mirror unit. In many circumstances they are a superior choice of reflector for terrestrial and space applications.
A mirror's capacity to accurately redirect light to a receiver is adversely affected by any slope errors of its reflective surface. This is true for all mirror types and, with the promising arrival of retroreflective material, where two reflections take place, control of surface angular errors becomes even more critical. As for multisurface mirrors, although kept to a minimum during production, slope errors have the cumulative effect of defocusing the character of concentrated light in the focal zone. The net result is a costly reduction in power availability at the receiver. A simple solution to this would be to shorten the distances that reflected rays must travel by placing the receiver much closer to the mirror surfaces. If this could be done, the effect of slope errors would then be greatly diminished, resulting in a more accurate mirror that would produce a more dense concentration of light at the receiver. This concept has never been exploited in the prior art. Previously, multisurface mirror focal lengths were kept long because, if the receiver was positioned too near the collector, major light losses occurred due to the blockage of reflected rays by adjacent mirror elements.
The "bypass" mirror elements of this invention make it possible to bring the receiver and mirrors much closer together than ever before, while nearly eliminating loss of light. It is intended that these reflectors be employed within the concentrating photovoltaic, photothermal and remote sensing technologies.